1. Field of the Invention
The present invention relates to hexagonal ferrite magnetic powder for magnetic recording and specifically to hexagonal ferrite magnetic powder for magnetic recording which is preferable as coating-type magnetic powder for a magnetic recording medium having high coated film durability.
Furthermore, the present invention relates to a method for producing hexagonal ferrite magnetic particles preferable for the production of the above-described magnetic powder and a magnetic recording medium having a magnetic layer including the magnetic powder.
2. Description of the Related Art
In the related art, for a magnetic layer in a magnetic recording medium for high-density recording, ferromagnetic metal particles have been mainly used. Ferromagnetic metal particles are acicular particles mainly containing iron, and, for high-density recording, a decrease in the size of the particles and an increase in the coercive force thereof have been pursued. Ferromagnetic metal particles have been used for magnetic recording media in a variety of uses.
Due to the increasing amount of information recorded, a magnetic recording medium always requires high-density recording. However, in terms of higher-density recording, a barrier begins to appear in the improvement of ferromagnetic metal particles. In contrast, hexagonal ferrite magnetic particles have a coercive force great enough to be used as a material for a permanent magnet and are capable of maintaining a high coercive force even when the particles are miniaturized since magnetic anisotropy which is a basis of the coercive force is derived from the crystal structure. Furthermore, a magnetic recording medium in which hexagonal ferrite magnetic particles are used for a magnetic layer has excellent high density characteristics due to a perpendicular component thereof. As described above, hexagonal ferrite magnetic particles are ferromagnetic bodies suitable for increasing the density.
In recent years, in order to further improve the above-described hexagonal ferrite magnetic particles having excellent characteristics, provision of a metal such as Al to particle surfaces of hexagonal ferrite has been proposed (for example, refer to JP2011-225417A).